This invention relates to flame-type leak detectors and more particularly to such a detector having greatly improved sensitivity permitting the location of very small leaks of refrigerant gases containing halogens.
For detecting leaks in large air-conditioning systems employing Freon refrigerants, it has been common practice to locate such leaks with a flame-type detector. Such leak detectors have essentially comprised a conventional propane-type torch provided with a copper-containing reaction element located so as to be heated by the torch flame. By bleeding into the air supply of the torch air flow drawn through a flexible search tube, the presence of Freon in the atmosphere at the distal end of the search tube could be detected by noting the effect such gases have upon flame in the region of the copper reaction element. As is understood in the art, the fluorine in the Freon refrigerant reacts with copper to produce a green tint in the normally blue flame. While the leak detectors of the type available heretofore would detect leaks substantially smaller than those detectable with a soap solution, very small leaks could not be reliably located.
As a result of the need for leak detectors capable of detecting very small leaks, electronic leak detectors were evolved which could be adjusted to obtain the desired sensitivity. Such detectors, however, were both expensive and, for the refrigeration technician, relatively complicated to operate. In particular, the apparatus had to typically be calibrated so as to offset the presence of Freon in the atmosphere generally, i.e. a signal which might be considered "background noise" in the electronic sense.
One difficulty encountered in locating small leaks with prior art flame-type detectors was the dilution of the sample by the relatively large amount of air required for satisfactory burner operation. Further, the presence of Freon in the general atmosphere around the burner could mask the effects caused by Freon in the sample, i.e., some greenish tint would be produced by the fluorine in the main flow of combustion air to the burner so that the effect of any increased concentration of fluorine in the atmosphere at the distal end of the search tube was greatly diluted. In accordance with the present invention, a very small burner is utilized, i.e., a burner of about 1/10 the fuel and air consumption of earlier detectors. The inability of prior art constructions to operate a such low levels is believed to be due to the inability of the burners to overcome the pressure drop of the search tube and to sufficiently heat a reaction element. The present invention overcomes these difficulties through a critical design incorporating a novel reactor arrangement.
Among the several objects of the present invention may be noted the provision of a flame-type leak detector which will detect very small leaks; the provision of such a leak detector which is relatively unaffected by background levels of Freon; the provision of such a leak detector which is highly reliable and which is rugged and simple to operate; and the provision of such a leak detector which is of relatively simple and inexpensive construction. Other objects and features will be in part apparent and in part pointed out hereinafter.